https://repository.kopri.re.kr/handle/201206/11904 2026-04-19T16:22:33Z 2026-04-19T16:22:33Z Lee, Ju Hyeon Kwon, Sae Yun Yin, Runsheng Motta, Laura C. Kurz, Aaron Y. Nam, Seung-il https://repository.kopri.re.kr/handle/201206/13609 2022-07-07T06:45:57Z 2021-10-01T00:00:00Z

Title: Spatiotemporal Characterization of Mercury Isotope Baselines and Anthropogenic Influences in Lake Sediment Cores Authors: Lee, Ju Hyeon; Kwon, Sae Yun; Yin, Runsheng; Motta, Laura C.; Kurz, Aaron Y.; Nam, Seung-il Abstract: Increasing mercury isotope ratios from pre-industrial (1510-1850) to present-day (1990-2014) in lake sediment cores have been suggested to be a global phenomenon. To assess factors leading to spatiotemporal changes, we compiled mercury concentration (THg) and mercury isotope ratios in 22 lake sediment cores located at various regions of the world. We find that the positive delta Hg-202 shifts together with THg increases from pre-industrial to present-day are a widespread phenomenon. This is caused by increased contribution of mercury from local to regional anthropogenic mercury emission sources, which lead to higher sediment delta Hg-202 (-1.07 +/- 0.69 parts per thousand, 1 SD) than pre-industrial sediments (-1.55 +/- 0.96 parts per thousand, 1 SD). The positive Delta Hg-199 shifts were observed in 15 lake sediment cores, which have low pre-industrial Delta Hg-199 (-0.20 +/- 0.32 parts per thousand) compared to the sediment cores with near-zero to positive pre-industrial Delta Hg-199 (0.08 +/- 0.07 parts per thousand). The magnitudes of delta Hg-202 (r(2) = 0.09) and Delta Hg-199 (r(2) = 0.20, both p > 0.05) changes from pre-industrial to present-day did not correlate with the magnitude of THg changes. Instead, the magnitudes of delta Hg-202 and Delta Hg-199 changes decreased with increasing pre-industrial delta Hg-202 and Delta Hg-199 values, suggesting that the baseline mercury isotope ratios play a more important role in determining the magnitude of mercury isotope changes compared to the degree of THg input. We suggest that the spatiotemporal assessments of delta Hg-202 in lake sediment cores can be used as an important proxy for monitoring changes in anthropogenic mercury sources for the Minamata Convention on Mercury.

2021-10-01T00:00:00Z Lee, Ju Hyeon Kwon, Sae Yun Lee, Hoin Nam, Seung-il Kim, Jung-Hyun Joo, Young Ji Jang, Kwangchul Kim, Haryun Yin, Runsheng https://repository.kopri.re.kr/handle/201206/13600 2022-07-07T06:11:10Z 2021-09-16T00:00:00Z

Title: Climate-Associated Changes in Mercury Sources in the Arctic Fjord Sediments Authors: Lee, Ju Hyeon; Kwon, Sae Yun; Lee, Hoin; Nam, Seung-il; Kim, Jung-Hyun; Joo, Young Ji; Jang, Kwangchul; Kim, Haryun; Yin, Runsheng Abstract: Despite the large climatic fluctuations in the Arctic over the Holocene, the dominant mercury (Hg) sources and the potential changes in Hg sources associated with the climate remain unclear. Here, we use Hg isotopes to reconstruct changes in Hg sources and processes in two Svalbard fjord sediment cores spanning the Holocene. The Hg isotope ratios of the fjord sediment cores are similar to bedrock and Hg bound to terrestrial total organic carbon (TOC) but different from other sediment cores influenced by atmospheric Hg drawdowns via the sinking of marine particulate organic matter. The absence of significant Hg and TOC relationships indicates that bedrock erosion caused by glacier dynamics is the major Hg source to the fjord sediment rather than those bound to marine and terrestrial TOC. Measurable shifts in Hg sources are observed at regional cooling (4.3 ka) and during the Medieval Warm Period in the late Holocene. The negative shift in delta Hg-202 (by -0.5 parts per thousand) at 4.3 ka from baseline (similar to 10 ka) is consistent with the rapid increase in glacier-mediated physical and chemical erosions of bedrock. The significant positive shifts in delta Hg-202 (by 0.5 parts per thousand) in the late Holocene are explained by enhanced input of atmospheric Hg and its drawdown via the sinking of marine particulate organic matter and some anthropogenic influence, which suppressed the positive Delta Hg-199 and Delta Hg-200 shifts. This study suggests that Hg isotope ratios measured in sedimentary archives can be used to decipher climate and other local to global changes modifying Hg sources in the Arctic.

2021-09-16T00:00:00Z Lee, Dong-Hun Kim, Jung-Hyun Lee, Yung Mi Kim, Ji-Hoon Jin, Young Keun Paull, Charles Ryu, Jong-Sik Shin, Kyung-Hoon https://repository.kopri.re.kr/handle/201206/13638 2022-07-08T01:25:25Z 2021-06-18T00:00:00Z

Title: Geochemical and Microbial Signatures of Siboglinid Tubeworm Habitats at an Active Mud Volcano in the Canadian Beaufort Sea Authors: Lee, Dong-Hun; Kim, Jung-Hyun; Lee, Yung Mi; Kim, Ji-Hoon; Jin, Young Keun; Paull, Charles; Ryu, Jong-Sik; Shin, Kyung-Hoon Abstract: During the ARA08C expedition in 2017, sediment push cores were collected at an active mud volcano (420 m water depth) in the Canadian Beaufort Sea from two visually discriminative siboglinid tubeworm (ST) habitats that were colonized densely and less densely (ST1 and ST2, respectively). In this study, we investigated the biogeochemical and microbial community characteristics at ST1 by analyzing the geochemical properties, microbial lipids, and nucleic acid signatures, and comparing them with the data previously reported from ST2. The two ST sites showed distinct differences in vertical geochemical gradients [methane, sulfate, dissolved inorganic carbon (DIC), total organic carbon, and total sulfur], with a higher methane flux recorded at ST1 (0.05 mmol cm-2 y-1) than at ST2 (0.01 mmol cm-2 y-1). Notably, the delta 13C values of DIC were more depleted at ST1 than at ST2, resulting in a higher proportion of DIC derived from the anaerobic oxidation of methane (AOM) at ST1 than at ST2. Moreover, both the ST1 and ST2 sites revealed the dominance of AOM-related lipid biomarkers (especially sn-2-hydroxyarchaeol), showing highly 13C-depleted values. The 16S rRNA analyses showed the presence of AOM-related archaea, predominantly anaerobic methanotrophic archaea (ANME)-3 at ST1 and ST2. Our results suggest that AOM-related byproducts (sulfide and DIC) potentially derived from ANME-3 were more abundant at ST1 than at ST2. This variation was attributed to the intensity and persistence of ascending methane. Therefore, our study suggests that AOMderived byproducts are possibly an essential energy source for tubeworms during chemosynthetic metabolism, shaping different colony types on the seafloor.

2021-06-18T00:00:00Z